Thermostat.



J. BOEKEL.

THERMOSTAT.

APPLICATION FILED FEB. 12, 1913.

1,094,362 Patented Apr. 21, 1914.

u iyfla WITNESSES I INVENTOR Allorueyo JULIUS BOEKEL, OF-PHILADELPEIA, PENNSYLVANIA.

THERMOSTAT.

Specification otLetters Patent. I

Patented Apr. 21, 1911,

Application filed February 12, 1913. Serial No. 747,911.

To all whom it may concern:

Be it known that I, JULIUS BOEKEL, a citizen of the United States, residing at Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented certain new and useful Im rovements in Thermostats, of which the ollowing is a specification.

This invention relates to thermostats of the mercurial type provided with means for mechanically raising or lowering the level of the mercury by means of a movable plun- -ger locked at an desired point to adjust the circuit closing evices according to the degree of heat at which an indication is desired. ,My Patent #983,345 discloses a good instance of such a thermostat. Y My present improvements relate principally to means for insurin perfect electrical contact at the point w ere the circuit is closed and preventing corrosion of the surface of the mercury; for preventing overflow of the merucry for reventing accidental short-circuiting by t e contact of certain parts with the operators finger and for permittin easy access to the contacts, though excluding foreign matter therefrom.

More particularly the said invention consists in a float carrying one of said contacts and provided with means for penetrating below the surface of the mercury, thereby preventing any break in the electrical circuit at. the point of contact between the float and the mercury, even if thesurface of the latter should becorroded; in providing an insulated do for an attachment of the float carrying the upper contact within the conducting'contact casing; in providing an annular mercury receiving groove in the up-- per end of the post on which the said casmg fits and in additional details of the thermostat, all as hereinafter more particularly set forth and claimed.

In the accompanying drawings: Figure 1 represents a front elevation of a thermostat embodying my invention, circuit W'ires a and I) being connected to their respective posts and of a battery in circuit, the said wires being broken away and the dust door being shown closed; Fig. 2, an enlarged vertical section of the upper part of the same; j Fig. 3, a cross-section of Fig. 2, taken just above the insulating annular guide; Fig. 41,; a detail perspective view of the movable: cylindrical door and the fixed cylindrical casing on which it turns, separated but ar- 1 insulating ranged in proximity to each other; and Fig. 5, a detail perspective View of the post on which the fixed metallic contact casing is screwed and which forms part of the guide for the float.

The mercury tube or reservoir 1 is of usual construction externally screw-threaded at the top to turn into' a recess 7 screw: tapped into the lower end of a c lindrical block 6 of insulating material, w ich may be considered the body of the thermostat. For the material of this .body any suitable below t e tube-suspending screw-thread above mentioned a collar 2 fitsti htly on said tube and is provided with a ra ial stud or screw-post 3 perforated at 1 to receive a wire which is held by 'a screw 5. In block 6 a vertical hole or passage 8-is provided for the mercury-adjusting plunger 12, which is locked in any position of vertical adjustment, as in the aforesaid patent, by a screw 11, working through the side of said block which is tapped to receive it. The height of the mercury de ends on the degree of immersion of said plhnger. The latter is of insulating material to contact with the operators finger, which has been found to occur when operating the ad'usting screw hereinafter described, provided a metallic rod be employed for said plunger, as has been usual hitherto.

material may be employed. Just prevent electrical The adjusting screw 13 of the upper electric contact of the circuit-making and breakscrew-threaded upper neck 17 of-a cylindrical metallic casing 18, which is internally screwthreaded at its lower end for turning home on a cylindrical integral upwardly extending broad post 19 of block 6, which post has an internal bore 20 for the float hereinafter described,.making it a gui'gle for said float. The neck 17 is provided/with a laterally extending stud or screw- 0st 21 perforated at 22 for the reception 0 wire 6, the latter being held by screw 23. V A look nut 24 on adjusting screw. 13 bears against the top of said,neck,""fastening said screw and its contact 25 at any point or degree of adjustat its upper end an annular shoulder 28, against which is fitted an insulating guide ring 29 having an internal metallic bushing 30, for guiding an upwardly extending integral rod 31 of an elongated cylindrical Steel float 32 convex at both its ends and having a needle form platinum contact 33 projecting from its lower end. The lower circuit making and breaking contact 3 (preferably of platinum) of the thermostat is embedded in the upper end of rod 31 andextends above the same. The metallic casing 18 is open in front as shown from the top down to a point considerably below the guide ring 29, except when closed by a concentric door'or shield 35, fitting on the exterior of said casing and adapted to turn thereon, said door being in the form of a cylinder cut away in part for a length and breadth corresponding to the cut away part of the said fixed casing 18. By turning this door to uncover the front of said casing access may be had to the contacts and proximate parts; by turning the said door to close the same, dust andother foreign matters are excluded, a consideration which has been found important in the practical working of the thermostat. The bore or well 20 hereinbefore described extends vertically down through said post 19 into the main part of the body or block 6 communicating through a small hole 37 with a recess in the bottom of said block, the side wall of which is internally screw-threaded to receive and engage the corresponding externally screwthreaded upper end of mercury tube 1. Said hole receives and guides the lower needleform mercury penetrating contact 33 of float 32.

This thermostat differs from the one described in Patent 983,345 most conspicuously in never breaking electrical contact between the mercury and any other part; both of the circuit making and breaking contacts being metallic. It has been foun that under the former plan the surface of the mercury would often become oxidized and the same was to some extent true of the contiguous metallic contact, which would be subjected to greater electrical stress and greater heat by increased resistance at this point, so that the electrical connection between thisoxidized surface and the metal above it was not reliable. By interposing the float which rises and falls with the mercury, and not relying on the latter to directly open and close the circuit, this danger is manifestly avoided. But, although this combination greatly lessens the oxidization at the point of liquid and solid contact, some oxidization of the mercury surface is always likely to occur from the normal action of the oxygen in the air and the surface thus oxidized becomes an unreliable conductor. It would of course be fatal to break the circuit at this point and the absolute reliability of electrical connection there becomes highly important. This is insured by the downward extending needle form contact of the lowerend of the float, which is continuously embedded in the mercury, penetrating below the oxidizable surface and insuring-constant electrical connection and unbroken current so long as the mercury extends up to (or nearly to) the shoulder 36, a matter which is readily controlled by the plunger 12. In practice the float will usually be held by the mercury above this shoulder to a greater or less degree, but it can in no case descend below said shoulder, as the lower end of the float is much greater in diameter than the lower contact pin 33 and forms a shoulder above it stopped by said shoulder 36. Although the hole 37 will guide this contact while the latter is within it such service is unnecessary as the wall of bore or well 20 fits closely enough to the body of the float to guide, without impeding, it. Usually this closeness of fit will prevent any of the mercury from passing up between these surfaces, but to guard against this loss of mercury from this cause, as well as against inconvenience in the operation of the thermostat I have provided an annular recess 38 in the top of post 19, for receiving any mercury which may be drawn up by said float or forced up around it. The subsequent removal ofthe mercury from this recess is of course very easy, without detriment to the thermostat. Of course it would be possible to substitute other fluid for mercury in such athermostat, in which case a float of lighter material than steel would preferabl be used, and I do not limit myself to t ese materials orto any others specifically, bein at liberty to substitute any metals or' ot er substances adapted to perform the same functions in such a device; but the instrument as described is practically the best. The general operation thereof is described in the said patent, to

which reference is hereby made. The operation of the various improvements now applied for has already been suificiently explained herein. The circuit is from wire a through tube 1 and its mercury to the float and the upper contact, theadjusting screw, the fixed casing, the lateral post and wire 6. lVhen the two cooperating metallic contacts separate there is no circuit.

A stud 38 on the fixed casing 18 prevents the shield or door 35 from turning too far in either direction. The edges of the said door are provided with two notches or recesses 39, one of which will fit on said stud in the closed position of said shield, the other rewhat I claim as new and desire to secure by Letters Patent is:

.ed to penetrate the oxidized surface of the mercury and the lower portion of said float being relatively broad and forming a shoulder above said contact pin.

2. In a thermostatic device forming part of an electric circuit, a float, in combination with means operated thereby for closing and opening said circuit, a mass of oxidizable conducting liquid under and in contact with said float, a contact pin of relatively smaller diameter extending centrally downward therefrom and adapted to penetrate the oxidized surface of the liquid and a fixed part throu h which said pin works up and down with 51c motion of the float.

3. In a thermostatic device forming part of an electric circuit, a float, in combination with means operated thereby for closing and opening said circuit, a mass of conductingliquid under and in contact with said float, a fixed body in which the said float moves up and down and a part of which extends under the said float, formin an annular shoulder surrounding a central ole, and a contact pin extending centrally down from said float through said hole and guided therein, said contact pin being adapted to penetrate the oxidized surface of the liquid and the lower portion of said float being of considerably greater diameter than that of said pin, so that the said annular shoulder will serve as a stop therefor.

4. In combination with a cylindrical float, a part in which said float is guided in its upward and downward movement and which is provided with a stop preventing said float from descending below a given point, a conducting liquid below and in contact with said float, circuit closing devices operated by said float,'and a downwardly presented contact 'pin carried by said float and extending below said stop when the float is in its lowest position and adapted to penetrate the oxidized surface of said liquid.

5. In combination with an expansible column of liquid, a float having a needle-form 'contact at its lower end adapted to penetrate the oxidized surface of said liquid, and provided at its upper end with an extended part carrying a contact, an insulated guide for.

said extended art, another contact arranged to cooperate erewith in closing the circuit and a casing surrounding these upper contacts.

6. In combination with a column of electrically conductin liquid expansible by heat and a receptacle t erefor, a float rising and falling with the same, circuit closing'devicesoperated by said float, a plunger adjustable in said li uid to raise or lower it, a contact pin exten ing down from said float and a stop under said float for limiting its downward movement, the lower end of'said float being of considerably greater diameter than that of said contact pin.

7. A thermostat body and depending mercury tube, incombination with a post raised on said body, externally screw-threaded and internall bored, a casing screwed on said post, a cat movable up and down in said ore and electrical circuit closing contacts, one of which is carried by said float, the said bore being extended down through the body and having a shoulder at its lower end, but communicating with the mercury in said tube and fitting the float so as to guide without impeding the same. 7

8. In combination with a mercury-containing tube, an insulating block rovided with a recess for receiving the end t ereof, a passage extending through said block to said recess, a bore or well extending down through said block and having a shoulder at its lower end, but communicating with said tube and a raised post containingthe upper part of said bore or well and externally screw-threaded, a plunger adjustable longi .tudinally through said passage, 5, contact carrying float movable in said bore or well and guided thereby, a casing screwed on said post and a contact mounted in said casing to cooperate with the contact thus carried.

9. In combination with the circuit-clos ng contacts of a thermostat and a float and expansible mass of liquid operating them, a fixed casing protecting said. contacts but having an opening, and a shield or door rotatable on said casing to open or close said opening at will, said casing being provided with a stoparranged for contact with the edge of said shield or door.

10. A float provided with a reduced upper extension carrying a contact and a mass of liquid below and in contact with the same, in combination with a fixed guide for said upper extension, 2. contact arranged to cooperate with the contact first mentioned, conductors making circuit through such contacts, liquid and float, and a downwardly presented contact pin of relatively small diameter carried by said float, the lower end of the float being of greater diameter, forming a shoulder above said pin-and the latter being adapted to penetrate the oxidized surface of the liquid when said float is thus stopped.

11. An electrically conducting float provided with a reduced upper extension carrying a contact, in combination with a mass of electrically conductingand expansible liquid under and in contact with said float, a fixed insulating guide for such upper extension, a contact arranged to cooperate with the contact first mentioned, conductors making circuit through said contacts, liquid and float, and a stop limiting the downward movement of said float.

12. A float having a reduced upper extension carrying a contact and also rovided with a contact extending down rom its lower end and of considerably less diameter than that of said float which forms a shoulesa-see der above it, guides for said extension and said lower contact, means cooperating with said upper contact to close the circuit, and a mass of expansible conducting liquid under and in contact with said fioat, said lower contact being adapted to penetrate the oXidized surface of said li uid.

In testimony whereof, I have signed my name to this specification in the presence of two subscribing witnesses.

JULIUS BoEKELQ Viitnesses':

JOHN H. SGHERER, Faun. MANGGLD. 

